1. Field
The present invention generally relates to techniques for operating an external storage array. More specifically, the present invention relates to a method and apparatus that controls a cooling fan for a storage array.
2. Related Art
Some external storage array manufacturers are working to increase the electrical efficiency of their external storage arrays, and cooling fans can be one source of inefficiency. Typically, cooling fans for external storage arrays are set to have a high nominal fan speed so that there is adequate thermal margin, even for an external storage array running at full load and at altitudes as high as 10,000 feet above sea level, where the air is thinner and less effective at cooling. Therefore, for external storage arrays operating in less extreme conditions, cooling fans may be running at higher speeds than required to adequately cool the external storage array. Reducing the nominal cooling fan speed may reduce the power used by the cooling fan, but since many external storage arrays do not have internal temperature measurement devices, controlling the cooling fan based on a measured temperature for the external storage array may not be possible.
Hence, what is needed is a method and apparatus that controls a cooling fan for an external storage array, without the above-described problems.